1. The Field of the Invention
The present invention relates to an improved artificial toe joint. More specifically, the present invention relates to an artificial toe joint providing increased durability and reduced damage to the surrounding bone.
2. State of the Art
Toe joints such as the proximal metatarsal phalangeal joint, the proximal most toe joint of the foot, may become damaged from injury, etc. and may then be replaced. As a toe joint is damaged and deteriorates, symptoms may include loss of propulsion, transfer lesions, metatarsalgia (pain and inflammation of the ball of the foot), gait alterations, pain, etc. Indicators for joint replacement include: hallux limitus, hallux rigidus, hallux abducto valgus, rheumatoid arthritis, osteoarthritis, previous surgery at the joint which is painful or which resulted in an instable joint, joint problems after a prior joint surgery, failed joint surgery, etc.
The interphalangeal joints and other joints of the toes may also become damaged, and it will be appreciated that the artificial joint of the present invention may also be applied to these toe joints as well. Specifically, the present invention can be used in the joints including, but not limited to the inter phalangeal joints of all lesser digits, as well as the metatarsal phalangeal joints of all lesser digits. It is appreciated that the fusion of these joints does not result in the same loss of mobility and the same degree of detriment to a patient as does the fusion of the proximal metatarsal phalangeal joint, but does result in some detrimental effects for the patient. For example, the second metatarsal phalangeal joint can develop Freiberg's infraction resulting in metatarsal head deformation and loss of cartilage. The treatments are generally limited following Freiberg's.
Furthermore, the invention is not restricted to the metatarsal phalangeal joint of the first digit and can be utilized to replace the inter-phalangeal joint of the first digit which too is often damaged secondary to cartilage loss and is often fused. As will be explained below, the present invention is suitable for both conditions as it allows resurfacing of the joint.
Currently, artificial metatarsal joints exist which are implanted by cutting off the ends of the bones which form the natural joint (typically the metatarsal phalangeal joint), reaming out the cut ends of the bones (the base of the proximal phalanx and the head of the metatarsal) to receive the stems of the artificial joint, and inserting the artificial joint. The prior art artificial joints place stress on the bone surrounding the joint, often resulting in destruction of the bone surrounding the joint and thus failure of the artificial joint. It is common for artificial toe joints to fail about five years after replacement. Once the joint has failed, the bone structure surrounding the joint (the cut end and hole into which the artificial joint has been inserted) has often degraded to where the joint must be fused together. It is easily appreciated that a fused toe joint is highly undesirable as it limits mobility, and may make it significantly harder for a person to accomplish daily tasks such as walking.
It is important to note that current joints generally cannot provide compensation for angular deviations at the first metatarsal phalangeal joint. Such deviations include, but are not limited to: hallux abductovalgus, inter phalageous angle, plantarflexed as well as dorsiflexed metatarsal head, intermetatarsal angles, and proximal articular set angle as well as the distal articular set angle. The advent of a total implant that can compensate for such deviations is very advantageous secondary to angular correction. These corrections will allow reduction of pain proximally in the foot as well as extend the life of the implant.
It is desirable that an artificial toe joint should achieve certain results. The artificial joint should be stable and provide stability to the patient, such as when standing and walking. The artificial joint should provide a pain free range of motion to the patient. The artificial joint should allow the patient to walk and move in a natural manner. It is desirable that installation of an artificial joint provide an increase in activity levels and an improvement in the lifestyle of the person. An artificial joint should provide long term success; promoting the strength of the surrounding bone and resisting deterioration of the resulting joint so as to minimize the need for the later fusing of the joint.
There is thus a need for an artificial toe joint which overcomes the limitations of available artificial toe joints. Specifically, there is a need for an artificial toe joint which has less affect on the bone structure around the joint. It is also desirable to provide an artificial joint which allows for angular deviation correction to reduce stress and strain proximally in the foot. It is also desirable to provide resurfacing of the existing anatomy which is low profile and anatomically similar to existing structures. Thus, there is a need for an artificial toe joint which provides greater long term success of the artificial joint and which replicates existing anatomical motion. There is also a need for an artificial toe joint which may be used in replacing a previously installed artificial toe joint which has failed to thereby eliminate the need to fuse the joint. There is a further need for an artificial toe joint which is easier to install. It will be appreciated that achieving any one of these will be an improvement in artificial toe joints, while achieving multiple of these ends would constitute a substantial improvement for patients.